The present invention relates to an apparatus for determining the amount of a coating material on a cylindrical surface.
In the production of many coated articles such as carpeting and paper, the coating composition, e.g., binder or sizing, is applied to the article's surface by the continuous transfer of said composition thereto from an applicator roll. Typically, in such application, the applicator roll rotates in a reservoir of the coating composition and applies the liquid film of the composition formed thereon to the article's surface, either directly or through a series of additional rolls.
In such operations, in order to effectively coat the article, i.e., impart thereto the desired physical properties such as printability to printed paper and dimensional stability and rigidity to a carpet structure, it is generally desirable to measure the amount of the coating composition on the applicator roll.
Heretofore, several apparatuses and methods have been proposed for determining the amounts of the coating composition on an applicator roll. For example, U.S. Pat. No. 2,951,416 discloses an apparatus useful for measuring the thickness of a liquid film on a moving member which comprises a film pick-up roll of a light transmitting material in peripheral engagement with the moving member, a light source for projecting light through the roll and a photoelectric means for measuring the light transmissibility therethrough. Unfortunately, such apparatus requires a substantial capital outlay. Moreover, due to the large amounts of highly reflective fillers, e.g., calcium carbonate, in many latex-based coating systems, this apparatus cannot be employed in conventional coating applications involving such composition.
Similarly, the amount of ink on a printing cylinder may be controlled by an apparatus comprised of (1) a radiation emitting means carried by the cylinder and adapted to pass radiation through a coating of ink thereon and (2) a radiation response means to measure the amounts of radiation transmitted by the coating. See, for example, U.S. Pat. No. 2,971,461. U.S. Pat. No. 3,130,303 discloses a similar type apparatus employing beta ray backscattering as a means of measuring the coating thickness on a roll. Unfortunately, such methods and apparatuses require substantial capital expenditure and cannot be suitably employed in many production operations.
Also known are several methods and apparatuses which control the amounts of a coating composition transferred from an applicator roll to a continuously moving web or strip of material, thereby indirectly measuring the amount of the coating material on the applicator roll. See, for example, U.S. Pat. Nos. 3,605,682 and 2,981,638. While these methods and apparatuses accurately measure and control the average amount of said composition transferred from the applicator roll over an extended period of time, they cannot effectively measure or control momentary deviations from the average.
In view of the aforementioned deficiencies of prior art methods and apparatuses, it remains highly desirable to provide an effective and economical apparatus and method for determining the amount of a coating material on a cylindrical surface, which apparatus can detect instantaneous changes in such amount.